Disclosed in U.S. Pat. No. 4,187,064 is a rotary motor/pump which includes a central shaft surrounded by an outer housing. The shaft has an outer peripheral surface having at least one lobe while the other housing has a generally cylindrical inner surface in sliding contact or located adjacent the lobe. The outer housing is also provided with a plurality of radially movable gates. The gates co-operate with the lobe to provide variable volume working chambers which receive a working fluid under pressure when the device is acting as a motor or which exhausts a fluid under pressure when the device is acting as a pump or compressor. Relative rotation occurs between the shaft and the outer housing to vary the volume of the chambers.
Earlier rotary machines included steam engines such as those described in U.S. Pat. Nos. 349,888, 389,328, 664,486, 1,900,784, 371,949, 398,988, 500,988, 590,581, 355,479, 604,709 and 866,677. Although a variety or rotary motors are described their configuration is such that they are unemployable in a drill string of a well formation.
Fluid pumps and/or fluid motors are described in U.S. Pat. Nos. 2,232,951, 3,426,694, 445,318, 3,134,335 and 3,241,456. Again although a variety of rotary machines are described they are unemployable in a drill string.
An internal combustion engine is known having a centre rotor with an outer housing, where the rotor is joined to the housing by means of radially reciprocating vanes. In one embodiment the vanes have rollers which engage a cam groove in the rotor. Again this device is unemployable in a drill string.